Persons suffering from chronic obstructive pulmonary disease (COPD) and others with various respiratory disorders often experience a decreased ability to inhale. For example, while a healthy person may develop a maximum inhalation pressure of approximately 80-100 cm H.sub.2 O, a person with a respiratory disorder may be able to develop a maximum inhalation pressure of only half that. As a means of rebuilding respiratory strength, physicians often prescribe a protocol of respiratory therapy involving inhalation resistance training.
In current respiratory therapy practice, it is useful to prescribe respiratory muscle training programs using simple flow resistance apparatus for specified training protocols over extended periods of time in the patients' homes. There has been no way to provide these patients with an indication of how much force to exert with their inspiratory muscles in order to insure an effect of the exercise. Furthermore, it is suspected that patients adapt their breathing pattern to minimize the effort of breathing and, thus, the effect of the prescribed protocol.
By providing patients with some type of indication of their performance during inspiratory exercise, it is believed that the exercise would prove to be more effective as it would tend to prevent conscious or subconscious cheating during the exercise. Measurement of patients' performance, however, is difficult due to the small pressures (5-20 cm H.sub.2 O) involved.